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| Dissertation / PhD Thesis/Book | PreJuSER-8301 |
2009
Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-598
Please use a persistent id in citations: http://hdl.handle.net/2128/15300
Abstract: Novel memory materials and concepts are in the focus of nowadays research activities because CMOS-based architectures are assumed to run into their physical limits by further downscaling of the minimum feature size. Hence, alternative resistive random access memories (RRAM) are of increasing interest. The core of the RRAM is a material which can be switched between two different resistance states by applying a threshold voltage. One state corresponds to logical “1” and the other corresponds to logical “0” building a binary non-volatile memory. A memory cell can be realised with a MIM-capacitor configuration in which the resistance switching material is sandwiched between two metal electrodes. The development of novel structuring techniques for the realisation of sub-100 nm feature sizes is a major key issue in the field of semiconductor technology. Especially the development of low cost systems which can offer nanometer resolution will become more important in the near future. Nanoimprint lithography is an alternative moulding method which offers high throughput and resolutions < 10 nm and is thereby pronounced as a future lithography candidate. This thesis describes the development of a nanotechnology platform based on nanoimprint lithography which can be used to fabricate RRAM architectures. Therefore glass wafers were patterned by electron beam lithography and reactive ion beam etching for the use as nanoimprint stamp. Afterwards a UV nanoimprint lithography (UV NIL) process was established. The imprint parameters (pressure, time, UV dose and temperature) were optimized regarding the mould layout. Effects of the resist thickness on the imprint quality were investigated. Dry etching processes were optimised to transfer nanostructures into metal layers and consequently to form nano metal electrodes. Crossbar memory architectures with line widths down to 30 nm were realised with the established processes. Furthermore, a multilayer crossbar array was built which demonstrates the potential for very high integration densities. This multilayer concept requires the planarization of each metal layer with spin-on glass, in this case methylsilsesquioxane. Methyl-silsesquioxane in combination with silver was additionally found as resistively switching material during this work. RRAM cells with integrated spin-on glass show very fast switching properties (10 ns switching) and high integration density potential in 100 nm half-pitch devices. These conditions are important for future memory applications. By using a silver doping process of the glass layer instead of silver electrodes it was possible to stack the methyl-silsesquioxane RRAM cells onto each other. Electrical measurements on stacked cells proved their functionality whereby a three dimensional memory concept with integrated spin-on glass for very high integration densities was successfully demonstrated.
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